• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.83-88
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• 2011

Magnesium alloys have been focussed for the applications for lightweight of vehicle and electronics due to their high strength, low specific density and good damping capacity. This paper deals with the creep strength of Mg-Nd-Zr-Zn alloy. For the alloy, pure magnesium(99.9%) was melt with atmosphere of $0.3%SF_6$ and $25%CO_2$. After melting, 0.3% of zinc was inserted to stir for 10min at elevated temperature of $770^{\circ}C$. Master alloys of Mg-15%Nd and Mg-15%Zr were stirred in furnace. The creep tests were performed to obtain creep rate and rupture in the temperature range of 200 to $220^{\circ}C$ and 280 to $310^{\circ}C$ at an applied stress of 156 to 172MPa and 78 to 94MPa, respectively. The deformation mechanism was predicted dislocation climb from measured apparent activation energy and stress exponent. Also the increaser the temperature and stress the lower the stress exponent and activation energy. Finally, LMP parameter gives good information for the predicted creep rupture life.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.2
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• pp.1-9
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• 1990

Since the reverse shape memory effect(RSME) was reported in a CuZnAl alloy, further study has been done on the mechanism of this phenomenon and reported that it occurs by the bainitic transformation. But the present authors revealed in the previous work that the RSME in a B2 CuZnAl alloy is not caused by the shear process involved in the bainitic transformation and also that the RSME takes place as the remaining ${\alpha}^{\prime}{_2}$ phase, which is two-step transformed strain induced martensite, is newly transformed into ${\alpha}$ phase. In order to provide further evidence in supporting the facts, thus, more detailed investigations have been carried out in a $DO_3$ CuZnAl alloy.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.721-728
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• 2012

This paper evaluates the reliability of creep rupture life under service conditions of Alloy 617, which is considered as one of the candidate materials for use in a very high temperature reactor (VHTR) system. A Z-parameter, which represents the deviation of creep rupture data from the master curve, was used for the reliability analysis of the creep rupture data of Alloy 617. A Service-condition Creep Rupture Interference (SCRI) model, which can consider both the scattering of the creep rupture data and the fluctuations of temperature and stress under any service conditions, was also used for evaluating the reliability of creep rupture life. The statistical analysis showed that the scattering of creep rupture data based on Z-parameter was supported by normal distribution. The values of reliability decreased rapidly with increasing amplitudes of temperature and stress fluctuations. The results established that the reliability decreased with an increasing service time.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1570-1578
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• 2022

During a severe accident, steam generator (SG) tubes undergo rapid changes in the pressure and temperature. Therefore, an appropriate creep model to predict a short term creep damage is essential. In this paper, a novel creep model for Alloy 690 SG tube material was proposed. It is based on the theta (θ) projection method that can represent all three stages of the creep process. The original θ projection method poses a limitation owing to its inability to represent experimental creep curves for SG tube materials for a large strain rate in the tertiary creep region. Therefore, a new modified θ projection method is proposed; subsequently, a master curve for Alloy 690 SG material is also proposed to optimize the creep model parameters, θ_i (i = 1-5). To adapt the implicit creep scheme to the finite element code, a partial derivative of incremental creep with respect to the stress is necessary. Accordingly, creep model parameters with a strictly linear relationship with the stress and temperature were proposed. The effectiveness of the model was validated using a commercial finite element analysis software. The creep model can be applied to evaluate the creep rupture behavior of SG tubes in nuclear power plants.

• Journal of Powder Materials
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• v.25 no.4
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• pp.302-308
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• 2018

A lean alloy is defined as a low alloy steel that minimizes the content of the alloying elements, while maintaining the characteristics of the sintered alloy. The purpose of this study is to determine the change in microstructure and mechanical properties due to the addition of silicon or tin in Fe-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P alloys. Silicon- or tin-added F-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P master alloys were compacted at 700 MPa and subsequently sintered under a $H_2-N_2$ atmosphere at $1120^{\circ}C$. The sintered density of three alloy systems decreases under the same compacting pressure due to dimensional expansion with increasing Si content. As the diffusion rate in the Fe-P-Mo system is higher than that in the Fe-P-Mn system, the decrease in the sintered density is the largest in the Fe-P-Mn system. The sintered density of Sn added alloys does not change with the increasing Sn content due to the effect of non-dimensional changes. However, the effect of Si addition on the transverse rupture strengthening enhancement is stronger than that of Sn addition in these lean alloys.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.109-113
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• 2002

A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.792-795
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• 2004

Despite is product that ship, vehicles, development equipment and Metal Bearing for plant equipment that is mass-produced by present domestic companies Cast White Metal Lining Bearing that is Bimetal Bearing standing 2 generation is accomplishing master and servant and this is foreseen to be used widely on industry whole in hereafter but Cast White Metal Bearing need minuteness processing, while price competitive power is depending on income from superior another thing area than itself manufacture already in advanced nation to lowdown that the technique is generalized widely, when take into account technology change aspect of industrial technology developing country, Go added value creation by deepening of price competition is judged to be difficult hereafter. Because domestic production and supply are wholly lacking almost in Metal Bearing Cladding that take advantage of these technology, Data-base about connection technology is weak with technique and Know-How for product. This research unites Back Steel and Aluminium Alloy different kind metal and make the Clad river studying technology about union of Gogangseong Dacheung metal bearing hereupon.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.64-67
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• 2009

Vibrational micro-forming of pyramidal shape patterns was conducted for an Al superplastic alloy, Al 5083 and a Zr-based bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$. A vibrational micro-forming system was specially designed for generating vibrational load by combining a PZT actuator with a signal generator. Single crystal Si micro dies with wet-etched pyramidal patterns were used as master dies for vibrational micro-forming. The micro-formed pattern height was increasing with increasing the frequency of the vibrational load. In particular, the vibrationally-microformed pattern height was similar or even higher than the statically-microformed pattern height when the load frequency exceeded about 125 kHz. It was also observed that the crystal grains affect the surface quality of the microformed pattern and the distribution of the pattern height in the die cavity array.

• Journal of Korea Foundry Society
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• v.30 no.5
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• pp.187-195
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• 2010

In this study, in order to obtain a useful guide line for design and production of automotive heat exchanger components made of 4343/3003/4343 aluminum clad sheets, it was aimed to improve the understanding about the grain refinement effect on brazing characteristic of the clad sheets. Al-10Ti master alloy was used for grain refinement of 3003 core alloy, and the Ti inoculation level was systematically changed up to 0.1 wt%. The three-layer aluminum clad sheets were fabricated by hot roll bonding process. The effect of grain refinement on brazing characteristic of the clad sheets was investigated by evaluating wettability, bonding strength and sagging resistance.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.299-302
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• 2005

Semisolid A356 slurries were prepared by electromagnetic stirring casting and by inoculation of Al-5Ti-B master alloy. As stirring time and addition of Al-5Ti-B are different, the grain size of the primary phase is different. Through the experiment of rheocast in a Buhler horizontal die casting machine, it was found that the finer the equiaxed primary dendrites, the smoother the die filling and better cast quality. Small equiaxed primary dendrite also results in less liquid segregation on the surface.